package com.shop.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;


//操作数据库公共类
public class BaseDao {
    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    //静态代码块，类加载就初始化
    static{
        Properties properties=new Properties();
        //通过类加载器读取对应资源
        InputStream is=BaseDao.class.getClassLoader().getResourceAsStream("db.properties");
        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }
        driver=properties.getProperty("driver");
        url=properties.getProperty("url");
        username=properties.getProperty("username");
        password=properties.getProperty("password");
    }

    //获取数据库连接
    public static Connection getConnection(){
        Connection connection=null;
        try {
            Class.forName(driver);
            connection=DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return connection;
    }

    //编写查询公共方法
    public static ResultSet execute(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet,String sql,Object[] params) throws SQLException{
        //预编译的sql在后面直接执行就可以了
        preparedStatement=connection.prepareStatement(sql);

        for (int i = 0; i < params.length; i++) {
            //setObject占位符从1开始，但是我们的数组是从0开始的
            //给sql语句下的占位符赋值
            preparedStatement.setObject(i+1,params[i]);
        }
        resultSet=preparedStatement.executeQuery();
        return resultSet;
    }

    //编写增删改公共方法
    public static int execute(Connection connection,PreparedStatement preparedStatement,String sql,Object[] params) throws SQLException{
        preparedStatement=connection.prepareStatement(sql);

        for (int i = 0; i < params.length; i++) {
            //setObject占位符从1开始，但是我们的数组是从0开始的
            preparedStatement.setObject(i+1,params[i]);
        }       
        int updateRows=preparedStatement.executeUpdate();
        return updateRows;
    }

    //关闭连接释放资源
    public static boolean closeResource(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet){
        boolean flag=true;
        if(resultSet!=null){
            try {
                resultSet.close();
                //GC回收
                resultSet=null;
            } catch (SQLException e) {
                e.printStackTrace();
                flag=false;
            }
        }
        if(preparedStatement!=null){
            try {
                preparedStatement.close();
                //GC回收
                preparedStatement=null;
            } catch (SQLException e) {
                e.printStackTrace();
                flag=false;
            }
        }
        if(connection!=null){
            try {
                connection.close();
                //GC回收
                connection=null;
            } catch (SQLException e) {
                e.printStackTrace();
                flag=false;
            }
        }
        return flag;
    }
}
